Restrictive Blood Transfusion Strategy with Trigger Hemoglobin
Clinical question: What effect does a restrictive hemoglobin transfusion trigger of <7 g/dL have on clinical outcomes compared to more liberal transfusion triggers?
Background: Blood transfusions are standard of care in managing anemia despite sparse evidence that they improve clinical outcomes. As more evidence mounts that blood transfusions are associated with worse outcomes, the threshold hemoglobin level for transfusion has decreased. The safest hemoglobin trigger for blood transfusion remains unknown.
Study design: Meta-analysis of randomized control trials (RCTs) and systematic review of observational studies.
Setting: Data from MEDLINE.
Synopsis: Pooled data from three RCTs, including 2364 patients, compared outcomes between a restrictive hemoglobin transfusion trigger of <7 g/dL with a more liberal trigger. The restrictive strategy resulted in decreased in-hospital mortality (RR 0.74, CI 0.6-0.92), total mortality (RR 0.8, CI 0.65-0.98), rebleeding (RR 0.64, CI 0.45-0.9), acute coronary syndrome (RR 0.44, CI 0.22-0.89), and pulmonary edema (RR 0.48, CI 0.33-0.72). Using the restrictive strategy, the number needed to treat to prevent one death was 33.
A second meta-analysis of 16 RCTs found that less restrictive transfusion strategies (triggers of 7.5 to 10 g/dL) were not effective in improving outcomes. A systematic review of observational studies suggested that normovolemic patients can tolerate hemoglobins of 5-6 g/dL without affecting oxygen delivery.
The primary meta-analysis was limited by the inclusion of adult and pediatric patients and different indications for transfusion (critical illness, gastrointestinal bleed), which could have introduced some bias. Although the safest transfusion trigger remains unknown, this study demonstrates that <7 g/dL is safer than more liberal triggers.
Bottom line: A restrictive blood transfusion strategy with hemoglobin trigger of <7 g/dL in patients with critical illness or bleeding significantly decreases rebleeding, cardiac events, and total mortality.
Citation: Salpeter SR, Buckley JS, Chatterjee S. Impact of more restrictive blood transfusion strategies on clinical outcomes: a meta-analysis and systematic review. Am J Med. 2014;127(2): 124-131.
